Thermoguard Fire Varnish Basecoat is a professional-grade, 2-pack water-based intumescent varnish designed to protect timber and wood-based surfaces from fire. When used with Thermoguard Fire Varnish Overcoat Exterior or Interior, it forms a clear or stained finish that complies with BS EN Class B s2 d0, as well as British Standards Class 1 and Class 0 for surface spread of flame.

Ideal for preserving the natural appearance of internal or external wood, the system expands in fire conditions to create a heat-resistant barrier, preventing ignition and reducing smoke and gas emissions.

✅ Use on bare or previously varnished wood
✅ Available for interior and exterior applications
✅ Part of a certified fire-rated coating system
✅ 2-pack (base + activator) - mix before us

Surface Preparation

• Ensure timber is clean, dry and free of oils, wax or contamination

• Max moisture content: 18%

• Abrade non-porous, sealed or varnished surfaces with medium-grade silicon carbide abrasive

• Fill gaps with intumescent mastic to prevent fire ingress

• For tanalised or preservative-treated wood, consult Technical Department

• For OSB or specialist substrates, seek guidance before use

Tech Data

*Overcoat risk increases after 4 days. If over 7 days, abrade and spot basecoat again before overcoating.

Directions for Use

• Mix thoroughly and allow to stand for 30–60 minutes before use

• Use product within 4 hours of mixing

• Apply 1 or 2 coats as specified

• Follow with Thermoguard Fire Varnish Overcoat – interior or exterior, clear or stained

• Avoid condensation, ensure airflow and dry conditions until fully overcoated

Not suitable for floor surfaces subject to foot traffic.

Apply using:

• Brush (synthetic bristle)

• Short-pile roller

• Spray (conventional or airless – consult for tip sizes)

Data Sheets / Downloads

Thermoguard Fire Varnish 2k Basecoat - TDS

Thermoguard Fire Varnish 2k Basecoat Base - MSDS

Thermoguard Fire Varnish 2k Basecoat Activator - MSDS

Thermoguard Woodstain Compatibility